The tenor of the national debate over immigration changed from the first minutes of Donald Trump’s speech in New York City on June 16 announcing that he was running for the Republican presidential nomination. “The US has become a dumping ground for everybody else’s problems,” the real estate magnate said. “When Mexico sends its people, they’re not sending their best. They’re not sending you,” he said, gesturing to the crowd. “They’re sending people that have lots of problems, and they’re bringing those problems to us. They’re bringing drugs. They’re bringing crime. They’re rapists.”

Here he interjected a brief qualifier. “And some, I assume, are good people.” But he returned quickly to his theme. “I speak to border guards and they tell us what we’re getting. And it only makes common sense,” Trump said. “They’re not sending us the right people.” His crowd cheered, delighted.

Mexican-American and other Latino organizations were outraged. Univisión, the national Spanish-language television network, dropped its telecast of Trump’s Miss USA and Miss Universe beauty pageants. The Ricky Martin Foundation withdrew a golf tournament from a Trump property. The Spanish-born chef José Andrés abandoned plans for a restaurant in a new Trump hotel in Washington.

But the rhetoric, far from damaging Trump, lifted him in the polls. He intensified it. In August he issued a six-page immigration plan—called Immigration Reform That Will Make America Great Again—homing in once again on Mexico, saying that its leaders had been “taking advantage of the United States using illegal immigration to export the crime and poverty in their own country.” “The Mexican government has taken the United States to the cleaners,” the plan complained. Trump said he would make Mexico pay for a wall to run the length of the two-thousand-mile border, and if Mexican leaders balked he would impound remittances to Mexico that were “derived from illegal wages.” He also proposed to put an end to the constitutional right to birthright citizenship—a child’s right to citizenship by having been born here—for US-born children of undocumented parents, which he said “remains the biggest magnet for illegal immigration.”

As these proposals proved popular with his ardent and growing following, Trump made immigration a fixture of his stump speech. In September at a rally in Keene, New Hampshire, he softened his statements, saying, “I love the Mexican people. I’ve had thousands and thousands of Mexican people that have worked with me over the years—thousands.” But then he insisted that “we are going to have to do something” about children he called “anchor babies,” by which, he made clear, he mainly meant Mexican infants. “They’re on the other side of the border. They have a baby that walks across the border because nobody stops anybody.”

He elaborated on his proposal to deport all 11 million undocumented immigrants in the United States. “Some people don’t agree, they think it’s harsh,” Trump told the crowd in Keene. “You know, Dwight Eisenhower was a wonderful general and a respected president, and he moved a million people out of the country,” Trump said, a reference to Operation Wetback in 1954, when Mexican farm guest workers who had been summoned to harvest American crops during World War II were sent back to Mexico in mass round-ups commanded by a former army general.

“Nobody said anything about it,” Trump said, lamenting that since then the historical moment had changed unfavorably for him. “When Trump does it, it’s like ‘ugh.’ When Eisenhower does it, that was fine, whatever, he was allowed to do it.”

Trump has given few details of how he would carry out his proposals. But his views on immigration became widely heard as his bombast captivated the media and he rode through the summer at the top of the Republican field in polls. His rivals had to adjust their positions to support or, at some risk, confront him. Governor Jeb Bush—who once described an illegal border crossing as an “act of love” by a parent seeking to help a family—retreated from his support for a path to citizenship for all undocumented immigrants, instead advocating a more cautious “earned legal status.”

Senator Marco Rubio backed off even further, after having been an author in 2013 of a comprehensive immigration bill that passed the Senate and included a long but direct pathway to citizenship. (That bill died in the House of Representatives.) Rubio said he had “learned” that “you can’t even begin to have a conversation” about legalization without first achieving much more conspicuous border enforcement. What he said seemed to amount to an indefinite postponement of legalization efforts.

Until the Trump campaign, the Republican Party—even in the House of Representatives, with its many conservatives—had been edging toward a pragmatic recognition that mass deportation of 11 million people was not a realistic option, and that the self-deportation alternative Mitt Romney had proposed as a presidential candidate in 2012 was a half-baked political confection that was unconvincing to hard-liners and offended many Latinos. It was a significant factor in Romney’s defeat.

Then Trump came forward with his unapologetic nativism, which included a call for a “pause” in legal immigration to the United States. He thrust into the mainstream of Republican policymaking restrictionist ideas that had been marginal for decades, encouraging the anger of Americans who have been wary of the country’s rapidly evolving demographic diversity and want action against what they see as an uncontrolled influx of outlaws.

Trump left no doubt that he was not afraid to alienate Hispanics. He expelled Univisión anchorman Jorge Ramos, a Mexican-American who is one of the country’s most prominent and popular Latinos, from a press conference (although a few minutes later he allowed Ramos to return). He even pulled out of an appearance at the US Hispanic Chamber of Commerce, which says it represents about 3.2 million Hispanic-owned businesses nationwide.

It took a figure of the stature of Pope Francis to break through to the American public with a different point of view. The pontiff wasted no time. “As a son of an immigrant family, I am happy to be a guest in this country, which was largely built by such families,” he said, in the first comments of his visit, at the White House on September 23. In Philadelphia the pope addressed Hispanic immigrants directly, urging them not to forget that “you bring many gifts to your new nation.” Francis exhorted them, “Do not be ashamed of what is part of you, your life blood…. By contributing your gifts, you will not only find your place here, you will help renew society from within.”

The pope’s visit also provided the opening for a Mexican-American whose brief star turn became a media sensation: five-year-old Sophie Cruz, in braids and a Oaxacan embroidered blouse. As Francis circled the Washington Ellipse in his popemobile, Sophie sprinted through the legs of his security guards until one of them finally lifted her up to receive a papal hug, allowing her to complete her mission: to give the pope a letter and a T-shirt asking him to support relief from deportation for undocumented immigrants—like her father.

It should not be surprising to see a new cycle of reaction against immigration in the United States. The rejection that Chinese, Irish, and Italian immigrants, among others, encountered in the past is familiar enough. Still, it seems remarkable in 2015 for an aspiring presidential candidate to base his campaign on a broad and visceral attack on one nationality, blurring lines between immigration, illegal and legal, and the large and varied society of citizens of Mexican origin. With his complaint that Mexico is “not sending us the right people,” Trump has potentially picked a fight with as many as 34 million Mexican immigrants or Mexican-Americans, almost two thirds of the 54 million Latinos who now make up 17 percent of the population of the United States.

Trump has raised a question that could well determine the outcome of the presidential contest: How will Latinos respond? For many Mexican- Americans, Trump’s campaign is nothing new. It fits within repeating cycles of attraction and rejection for Mexican immigrants in this country and connects with a long history of challenges that citizens of Mexican descent have faced to their place in the society.

Mexicans are unique among the nationalities in the immigrant mix, since they are at once among the oldest and the newest of the country’s foreign-born populations. Many Mexican-Americans can trace their heritage to ancestors who inhabited what is now the US Southwest during the years before the Treaty of Guadalupe Hidalgo in 1848, when Mexico, defeated in war, ceded lands extending from Texas to California and as far north as Utah. They started out in this country not as immigrants but as subjects of conquest, even though under the terms of the treaty, the scattered population of less than 100,000 Mexicans in the immense new territory automatically became American citizens if they chose to remain.

Since the late decades of the nineteenth century, Mexican-American communities have been renewed and increased by waves of immigration. Mexican immigrants have been accepted, sometimes even welcomed, as laborers. Then during economic downturns they were vilified, and expelled when their labor was deemed unneeded. Until quite recently the border between Mexico and the United States was more or less porous: patrolling was haphazard until well into the twentieth century and the military-style enforcement that exists today has been built up only since the 1990s. After the most recent immigration surge, which started in the late 1980s and began to wane after 2008, about 11.5 million Mexicans are by far the largest immigrant group, according to the Pew Research Center; they make up one quarter of all foreign-born people in the United States.

Neil Foley, a historian at Southern Methodist University, has provided in Mexicans in the Making of America a usefully compact yet abundantly revealing history of those Mexicans and their continuous battles to secure their position here. He describes, for example, an immigration cycle a century ago and the backlash it generated, which took the form of a racial attack. In the 1920s an expanding American economy drew hundreds of thousands of Mexican migrant laborers, including many who crossed the border illegally. Foley chronicles a dispute the influx provoked in the congressional delegation from Texas. Representative John Nance Garner, who represented a district along the border, argued that Mexicans had integrated well in southern Texas and the region’s agriculture depended on them. “They will do necessary labor that even a Negro won’t touch,” Garner said.

He was opposed by John Box, a congressman from northern Texas, who wanted the state to be preserved “as the future home of the white race.” Box said that he would not allow Texas to become a “dumping ground for the human hordes of poverty stricken peon Indians of Mexico.” The concerns of Box and other politicians of similar views became part of a brew of fears that led to the passage by Congress in 1924 of major legislation establishing national origin quotas for immigration and reinforcing older statutes limiting US citizenship to “free white” persons and those of African origin.

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Sophie Cruz, an American citizen and the daughter of undocumented immigrants, approaching Pope Francis, Washington, D.C., September 2015

In subsequent decades many Mexicans were accepted by the legal system as white. Nevertheless, Foley recounts, in everyday life Mexican people faced harsh segregation. Throughout the Southwest, “No Mexicans” signs hung on restaurants and stores. At the courthouse in Cochran County, Texas, a sign over the bathroom instructed: “For Whites, Mexicans Keep Out.” Even Mexican diplomats felt the sting. Foley discovered in his archival research that a consul in Houston was informed by one restaurant owner that he would only be served in the kitchen. Another diplomat was told by a Catholic church that it would not baptize his child.

Discrimination persisted although as many as 500,000 people of Mexican descent served in World War II. They included up to 14,000 Mexican immigrants who were drafted although they were not American citizens; one of them, according to Foley, was General Eisenhower’s personal cook. After the war ended, Mexican veterans who had not been naturalized during their service were required to show that they had originally entered the United States legally. Despite honorable discharges, thousands who could not show legal status were deported.

Veterans like Sergeant First Class Ysaias Morales, whose honors included three presidential citations, were refused service at restaurants. The wife of Felix Longoria, a Mexican-American private killed in the Philippines during the war, received his remains in 1948 and sought to bury them in a town near San Antonio. The funeral home manager turned her away, saying that “other white people object to the use of the funeral home by people of Mexican origin.” But in a sign of changes soon to come, Longoria’s case was taken up by the American GI Forum, an organization Mexican-Americans created after the war to deal with such discrimination. From there, the case attracted the attention of the junior senator from Texas, Lyndon Johnson. “I deeply regret to learn that the prejudice of some individuals extends even beyond this life,” Johnson wrote in a telegram to the Forum. He arranged for Longoria to be buried in Arlington National Cemetery.

Despite the backdrop of prejudice, the labor demands of the war and the postwar expansion brought a new round of efforts to draw workers from Mexico. The Bracero Program, which started in 1942 and continued until 1964, brought in more than 4.5 million laborers on temporary contracts, mainly to American farm fields. Wages were kept low and reports of abuse of the workers were frequent. A Mexican official whom Foley cites found several thousand braceros in Arkansas living with no plumbing or kitchen facilities in “a state of semi-slavery.”

Yet demand for agricultural labor outstripped the supply of legal braceros after the war and illegal immigration surged again. Once again, Foley writes, it provoked a reaction. An influential radio broadcaster in Los Angeles, B. Tarkington Dowlen, demanded the removal of Mexican farm laborers from California, saying they were afflicted with syphilis and “inherently dishonest.” Such rhetoric set the stage for the wholesale round-ups of Operation Wetback in 1954, led by General Joseph Swing, who had won Eisenhower’s admiration as commander of the 11th Airborne Division during the war. In coordinated attacks, Swing sent military troops, state police, and Border Patrol agents through Mexican communities, carting people away in truckloads for summary deportation.

Along with his saga of intolerance, Foley also traces the efforts of Mexicans to resist and advance. The tenacious lucha, or struggle, of Cesar Chavez to organize farmworkers in California was an episode in which the interests of Mexican-Americans and Mexican immigrants diverged. The founder of the United Farm Workers was a Mexican-American from Arizona who had spent part of his childhood on the California migrant trail harvesting crops. He launched his campaign to unionize grape pickers in Delano in 1965. On the organization’s banners, he used Mexican symbols, among them the image of the Virgin of Guadalupe surrounded by her luminescent cloak. But the Bracero Program had undercut wages for his farm workers, and newly arrived Mexicans were recruited by growers as scabs.

However, Chavez’s campaigns were about more than fair wages for farm labor. In 1968 he undertook a fast that lasted twenty-five days and raised him to national attention. On the day when Chavez, wrapped in blankets, broke his fast, it was Robert Kennedy, then a Democratic presidential candidate, who handed him morsels of bread. “The world must know, from this time forward, that the migrant farm worker, the Mexican-American, is coming into his own rights,” Kennedy said. The farmworkers were winning “a special kind of citizenship…. You are winning it for yourselves—and therefore no one can ever take it away.”

Chavez became Mexican-Americans’ most recognized figure. But more than any activism, a piece of legislation passed by Congress in 1965 had a lasting impact on empowering Mexican-Americans. The Immigration and Nationality Act transformed the immigration system and, over the next fifty years, gave Mexican-Americans an irreducible advantage: strength in numbers.

The law eliminated the national origin quotas, opening immigration to newcomers from around the world, and placed a priority on bringing family members of American citizens and legal residents who were already in the United States. This was especially favorable to Mexicans, with so many of their families settled here. Over the next five decades about 16 million Mexicans came, about 28 percent of all new immigrants, by far the most from any nation, according to the Pew Research Center.

Tom Gjelten, a longtime correspondent for National Public Radio, has written A Nation of Nations, about the 1965 law and its aftermath, in time for its fiftieth anniversary in October. With careful reporting and a storyteller’s feel for narrative, he reconstructs the grand deal-making that yielded the law President Lyndon Johnson signed on New York’s Liberty Island. He also goes deep into the lives of a half-dozen immigrant families in Fairfax County, Virginia, describing how they doggedly go about creating the better future they were seeking in the United States, even when the country makes nothing easy for them.

Although Gjelten’s focus is not on Mexicans or illegal immigration, the book has rich insights for the current debate. In revisiting the 1965 negotiations, he discovered that none of the politicians and activists behind the law’s passage had any notion of its future impact. In signing the law, President Johnson assured the public that it was “not a revolutionary bill…. It does not affect the lives of millions.” Indeed, the new priorities on family reunification were largely the handiwork of an Ohio congressman, Michael Feighan, whose goal was to ensure that the immigration system continued to deliver mainly northern Europeans. As it turned out, half of all newcomers in the next five decades were from Latin America; today, according to the Pew Research Center, Europeans are only 10 percent of new arrivals. The demographic shifts that made Mexicans and other Latinos the fastest-growing minority—the result of the emphasis on uniting families—were a legislative accident.

Gjelten also shows the gritty drudgery of immigrants’ working lives and the high personal costs they pay to join American society. A Latina from El Salvador, Marta Quintanilla Call, left two small sons behind and on her way to an illegal border crossing suffered a series of sexual assaults by a macho smuggler. She labored as a motel housekeeper and a cashier, always scrimping and fending off predatory local Salvadoran street gangs. “It doesn’t offer money,” she said of the United States after two decades here. “That’s a lie. You have to work hard to live here.”

But Quintanilla Call eventually purchased a house for her parents in El Salvador, made a stable marriage to an American citizen, and brought her sons legally to the United States. “If you want to see the fruit, first you have to sow the seed,” she would say. As soon as she could pass the naturalization test, she became a citizen herself, determined to vote. Now she also has a stake in the tone and substance of the immigration debate.

After 1965, the immigration laws were subject to new cycles. A revision in 1976 drastically reduced legal channels for Mexican workers to immigrate, leading to another illegal surge. The amnesty of 1986 gave residency to about three million immigrants, mostly Mexicans. But it did not create new legal channels, and illegal immigration grew again.

Nevertheless, several scholars who write about Latino immigrants today are optimistic about their progress and their prospects. In a pivotal change, they find, over the last decade Mexican-Americans and other Latinos have begun to unite in an emerging national identity that is binding them together as a national political force.

Mario T. García, a historian at the University of California at Santa Barbara, calls them the Latino Generation, after getting to know some of them in his classes. With a paternal pride, he assembles simple oral histories of thirteen members of the cohort, mostly young people in their twenties. In a minimal but instructive analysis, García describes them as progeny of the 1965 immigration law, whose parents joined the flow from Latin America and the Caribbean. Sturdy families led by strong-willed parents are a common factor in their success at rising above poverty. “I don’t want my dad to have three jobs the rest of his life,” a Mexican-American woman, Cindy Romero, says, explaining what drives her.

Many of the parents came illegally. But crucially for the children’s advancement, most of them eventually acquired legal status. The young people are going to college in significant numbers, García writes, “a totally new historical experience” for Latinos in the United States. They speak English, often as a first language. They are “in fact acculturating and working to become very much a part of this country that unfortunately still does not embrace them as full Americans,” he insists.

At the same time, they are “more and more identifying themselves as Latinos in the public sphere.” Coming of age just as they became the largest minority, they “realize the enormity of their numbers.” And most have considerable experience with political hostility, having grown up amid angry disputes like the failed Proposition 187 in the 1990s in California, an effort to restrict public benefits for undocumented immigrants. “Even those born in the United States have had to define themselves in part in reaction to neo-nativism,” García writes.

An even more upbeat prognosis comes from Matt Barreto and Gary M. Segura, scholars who are also founders of Latino Decisions, a polling research organization. The surveys they present in Latino America have convinced them that this Latino generation is ready to become a decisive force in American politics.

They cite “a mountain of evidence” that common views and experiences among different groups—Mexican-Americans, Puerto Ricans, even Cuban-Americans—are creating a common identity and an “increasingly unified and empowered population.” They note that 93 percent of Latinos who are under eighteen today are American citizens. By their count, every month more than 73,000 Latinos become old enough to vote. “The demography,” they write, “is relentless.”

Michelle Frankfurter

The US Border Patrol apprehending migrants, Rio Grande Valley Sector near McAllen, Texas, April 2013; photograph by Michelle Frankfurter from her book Destino, published recently by FotoEvidence

Their research addresses the risks for Republicans in Donald Trump’s campaign. While jobs and education are more pressing concerns for many Latinos, the immigration debate is “a critical dynamic” motivating their votes, Barreto and Segura say. At the same time, “perceived attacks on the community” have an effect of unifying all Latino groups. “For the GOP to fend off the electoral consequences of demographic change,” they write, “the party must persuade those Latino voters who are open to supporting Republican candidates that the age of hostility is over.”

That is the opposite of Trump’s approach. His characterization of Mexican immigrants as criminals and sex offenders is insulting but also inaccurate, going against a consensus of academic research showing that Mexicans have far lower incarceration rates than Americans. But more alarming to many Latinos are Trump’s threats to deport millions of Mexican immigrants and require them to take their American-born children with them, ignoring that it is illegal to deport an American citizen. Although a mass purge may sound outlandish, for Latino immigrants the possibility is not remote. While the pace of deportations has slowed in recent months, they continue to be a fact of life in Latino communities. During the last seven years the Obama administration has deported more than two million immigrants.

Probably most offensive of Trump’s tactics so far is his having made the repeal of birthright citizenship a central issue of his campaign. Immigrants know the term “anchor baby” is a misnomer, since US-born children cannot help their parents immigrate until the children turn twenty-one years old. It seems unlikely that Trump could mobilize the huge national push it would take to amend the Constitution. Rather, the effect of his proposal is to cast doubt on the legitimacy of the citizenship of many Latino children.

Not surprisingly, 72 percent of Latinos have a negative view of Donald Trump, according to a recent poll by NBC News, The Wall Street Journal, and Telemundo. But with the Republican campaign in flux, it is still early to predict what lasting effect he will have on Latino voting. Dr. Ben Carson, the neurosurgeon who has pulled ahead of Trump in some polls, has said he does not favor swift deportation for undocumented immigrants. Instead, “after we seal the border,” he said in the Republican debate on September 16, he would offer them a chance to become guest workers, primarily in agriculture, with no prospect of citizenship. Those who declined would “become illegal, and as illegals they will be treated as such.” Senator Rubio, a Cuban-American, is also rising, and he could attract Latino votes.

Some Latinos could be discouraged from participating in the election. But a glimpse of a more likely outcome was provided by the sprint across the Washington Ellipse by Sophie Cruz, who happens to be the US-born child of undocumented parents—in Trump’s terms, an anchor baby. Leaders of the Hermandad Mexicana Transnacional, the organization that brought Sophie and her father Raúl to Washington, said in interviews that they had been planning an effort to make contact with Pope Francis for months. Sophie, the organization said, had composed her message herself ahead of time, committing it to memory. She wanted immigration reform so that her father would not have to worry about deportation and, she believed, would have more time to spend with her. “I have the right to live with my parents,” she said.

In recent years organizations like the Hermandad have grown and connected as never before into national advocacy networks. This year, many of those groups have turned their energies to voter registration, drawing on the anger Trump has provoked. Tens of thousands of legal immigrants have become naturalized in recent months. Thanks to Trump, Latinos may finally in 2016 achieve the electoral power that is the promise of their history and immigrant destiny.